From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The potential causes for the Autovac petrol feed float overfilling and failing.
| Identifier | ExFiles\Box 40\4\ Scan192 | |
| Date | 30th December 1926 | |
| S/W. Hs.{Lord Ernest Hives - Chair} X3579 CWB10/GM/30-12-26. AUTOVAC PETROL FEED. Thank you for your Hs{Lord Ernest Hives - Chair}3/LG22.12.26 on the above matter. The conclusions we arrived at were the same as your own, i.e., that if the float approximately 75% filled with petrol it would no longer drain itself, but we have been unable to establish the manner in which this condition was caused. Building We have thought it might be caused by a gradual holding up of the petrol level inside the float due to a large leak, or possibly to some obstruction in the hollow stem of the float which causes more than usual resistance to the petrol being sucked out on the suction period of the apparatus. We have thought it might be due to some particular manner of using an engine. For example, the Inspection Department strongly recommend that engines should be turned over at regular intervals when the car is not in use. Suppose now that the conditions are such that it takes three complete working cycles of the autovac to completely exhaust the petrol which has leaked in and which will stand at the same level inside and outside of the float. Suppose now, that in turning the engine the autovac is only worked through one cycle, then only one-third of the amount of petrol it contains will be extracted from it and the new petrol level in the working chamber will be higher by the depth of petrol left in the float than formerly, so that after resting again the petrol level through the system will have been increased by the amount left in the float. If this process is repeated at intervals of two or three days it will not take very long before the petrol level in the float has been built up to 75% of total capacity after which it no longer functions. The whole of this article presupposes a state of affairs in which it takes more than one working stroke of the autovac to completely empty the float. CONT: | ||